High speed transfer system

ABSTRACT

A High Speed Transfer System which comprises three Protection and Control devices. A first and a second of said Protection and Control devices are used for failure detection on the feeder bus-bar; the third of said Protection and Control devices is used for the High Speed Transfer System co-ordination functionalities.

The present invention relates to a high speed transfer system forElectrical Distribution, and, in particular, to a high speed transfersystem for Protection & Control of distribution networks.

The typical architecture of a High Speed Transfer System is showed inFIG. 3, in which a single device implements the High Speed TransferSystem function.

In particular, specific devices protect the two feeders bus-bar byimplementing specific protection functions.

In case of a failure on one feeder bus-bar, such devices send a trigger,via conventional input channels, to the High Speed Transfer Systemdevice which elaborates this information together with other informationregarding the bus-bar voltages. As the voltages are such to act on theswitchgear then the High Speed Transfer System device acts it.

This device is able to acquire the digital and analogic input signals bymeans of different electronic boards that have a DSP processor on them.Moreover it must process the entire High Speed Transfer System logic inorder to send the right output to the switchgears.

In order to face the temporal constraints due to the characteristicelectric system transients, such a device is very powerful from thepoint of view of the hardware components.

In same cases it is possible to implement on such device even theprotection functions. This is possible because the hardware allows to dothat.

The High Speed Transfer System devices currently used have however somedisadvantages, which are highlighted below.

-   -   The High Speed Transfer System devices currently used nowadays        are usually very expensive because they need a great hardware        power;    -   The communication among this device and the protection devices        is not very fast;    -   The hardware and the software requirements of this device are        not very efficient. To provide for this shortage, it is        necessary to increase the power of the hardware components with        a consequent cost increase;    -   A device structured in such a way is not very flexible in terms        of configuration for its customization. That means that the        customer can modify its configuration only with difficulties,        and only after it has been installed on the field.    -   The High Speed Transfer System logic is moreover based on one        function block execution cycle. There can be more than one        cycles, with different priorities, but the architecture is        anyway simply cyclic. This implies to improve the hardware        performances to face the temporal constraints. Consequently the        hardware complexity needs to be increased, with a corresponding        increase of its costs.

The goal of the present invention consists in the realization of animproved High Speed Transfer System and devices.

This goal is achieved by realizing a new High Speed Transfer System inwhich three Protection and Control devices are used, instead of thesingle one described in the previous sections. Two of the threeProtection and Control devices are used as protection of the feederbus-bar and the third one for the switchgear co-ordination.

Moreover in this new system an efficient software High Speed TransferSystem logic management is implemented, by splitting such logic into twoparts: one is implemented with cycles and the other one by means ofevents, or asynchronous respect the cycle part.

The invention will be now described in details with reference to theenclosed FIGS. 1, 2 and 4.

Referring to FIG. 1 and FIG. 2 it is possible to see the architecture ofthe three Protection and Control devices.

The two feeder Protection and Control devices acquire from the feederbus-bar the current and voltage measures in order to detect any possiblefailure on these bus-bar.

The same voltage measures are acquired also from the third Protectionand Control device, which realizes the High Speed Transfer Systemco-ordination. Such measures are necessary in order to identify theright instant time in which any switchgear operation must be carriedout.

The two feeder Protection and Control devices communicate to the HighSpeed Transfer System device any possible failure, for instance viaoptical cable as communication media.

An additional digital communication channel is used for the servicecommunication among the different devices.

The software architecture of the third Protection and Control device,i.e. the one realizing the High Speed Transfer System co-ordination, isstructured in order to allow both the cyclic execution of specific taskswithin their temporal constraints and the quick re-action to externalevents.

Some of the advantages of this High Speed Transfer System according tothe present invention are reported below:

-   -   The entire system is certainly cheaper than the system currently        used in the art, since in the system according to the present        invention use is made of three cheaper devices that do not        require a great hardware power. In fact all the different High        Speed Transfer System functionalities are distributed on the        three devices, which communicate among them.    -   The communication among the three devices, for the High Speed        Transfer System scope, is very fast because optical cable can be        used so to have a wide band communication channel. This implies        that the software has less temporal constraints because the        acquired information from the High Speed Transfer System        Protection and Control device are available sooner and        consequently there is more time to process such informations.    -   The hardware and software structure of these devices is very        efficient. The hardware structure is just able to perform the        High Speed Transfer System proper working functionalities. In        particular the software structure is very efficient. In fact it        is structured in two parts: one of which is performed in        software cycles while the other one is performed with events.        This solution allows to face the temporal constraints due to the        electric transients.    -   Finally the system according to the present invention is very        flexible in terms of configuration and consequently in terms of        customization. In fact the software is configurable in an easy        way from the Human Machine Interface of each Protection and        Control device, by implementating the specific functionality on        each of them.

A detailed description of the functionality is given in FIG. 1 and inFIG. 2. Each of the feeder Protection and Control device acquires fromthe feeder bus-bar the current and voltage measures in order to detectany possible failure on these bus-bar. Such failure is detected byimplementing specific protection functions able to distinguish thedirection of such a failure. In fact for failure of the electric loadsthe High Speed Transfer System does not have to intervene. The samevoltage measures are acquired also from the third Protection and Controldevice, which realizes the High Speed Transfer System co-ordination.Such measures are necessary in order to identify the right instant timein which any switchgear operation must be carried out. This is carriedout to reduce as much as possible any current and voltage overbump.

The High Speed Transfer System logic is different for the two casesrepresented in FIG. 1 and FIG. 2.

In the case represented in FIG. 1, as a failure occurs on the activefeeder bus-bar, the corresponding feeder Protection and Control devicesends to the High Speed Transfer System Protection and Control device atrigger signal, e.g. via an optical cable.

Such trigger signal is treated as an event from the High Speed TransferSystem Protection and Control device, so it is instantaneouslyconsidered from the software running on this device. The softwareprocesses such information in parallel to the rest of the High SpeedTransfer System functionalities, so to manage in the most efficient wayall the other High Speed Transfer System functionalities that must becarried out anyway.

As the right instant time for the switchgears operation occurs, thenthis device co-ordinates the opening of the switchgear on the feederbus-bar on which the failure occurred and closes the other one so toguarantee the power feeder to the electric loads.

Then the High Speed Transfer System Protection and Control device sendto the two feeder Protection and Control devices an informationregarding the changed configuration of the electric system so to informthem about that. In this way these two devices can interpretate in theright way the changing of the current and voltage measures due to theclosure and opening of the two switchgears. In the case of FIG. 2 boththe feeder bus-bar are active until on one of them a failure occurs.Even in this case the regarding feeder Protection and Control devicesends to the High Speed Transfer System Protection and Control device atrigger signal via the optical cable. Such trigger signal is treated asan event from the High Speed Transfer System Protection and Controldevice so it is instantaneously considered from the software running onthis device. The software processes such an information in parallel tothe rest of the High Speed Transfer System functionalities so to managein the most efficient way all the other High Speed Transfer Systemfunctionalities that must be carried out anyway.

As the right instant time for the switchgears operation occurs, thenthis device co-ordinates the opening of the switchgear on the feederbus-bar on which the failure occurred and closes the switchgear on thebus-bar on which the whole electric loads are connected, so to guaranteethe power feeder to those electric loads previously connected with thefailured feeder bus-bar.

Then the High Speed Transfer System Protection and Control device sendsto the two feeder Protection and Control devices an informationregarding the changed configuration of the electric system so to informthem about that. In this way these two devices can interpretate in theright way the changing of the current and voltage measures due to theclosure and opening of the two switchgear.

The difference between the two cases consists on the logic configured soto manage in the opportune way the three switchgears: the operationregard a couple of switchgears at a time.

Finally the digital communication via binary I/O is used to exchangeservice information among the three devices such as current and voltagemeasures, start and trip protection information, etc.

With reference to the software architecture of the third Protection andControl device, i.e. the one realizing the High Speed Transfer Systemco-ordination, is structured in order to allow both the cyclic executionof specific tasks within their temporal constraints, i.e. the High SpeedTransfer System cyclic part, and the quick re-action to external events,i.e. the High Speed Transfer System event-driven part. These two typesof processes are shown in FIG. 4.

Both of them have to interact with data structures and externalinterfaces, e.g. the analog and digital I/O, the analog part of the HighSpeed Transfer System algorithm.

High Speed Transfer System cyclic part containing part of the High SpeedTransfer System logic, e.g. switchgears opening logic, has to beperiodically executed within particular temporal constraints, forinstance 10-15 ms. In each cycle all the inputs are acquired, everyfunction block, composing this part of the High Speed Transfer Systemlogic, is executed and then the outputs signal are actuated. It is veryimportant that the time interval needed to complete a single cycle isless than a given maximum value in order to keep real time constraints.

High Speed Transfer System event-driven part contains all those part ofthe High Speed Transfer System logic that can not be executed in theCyclic part. This can be:

-   -   that part of High Speed Transfer System logic that must be        executed in correspondence of specific events, which need a fast        re-action time, in particular a re-action time less of the        cyclic part. If this part of logic were implemented in the        cyclic part its time re-action constraint would not be met.    -   that part of High Speed Transfer System logic that could be        executed as cyclic part but that would compromise the cyclic        part time constraints.

In order to fulfill these requirements, a software architecture as shownin FIG. 4 can be used.

Let's suppose that an external event happens. An interrupt serviceroutine is executed; it generates on its turn an operating system eventin order to awake a specific task able to manage this specific externalevent just happened. The operating system scheduler then will executethis task depending on its priority with respect to the other tasks.

Managing external events directly in the interrupt service routine (ISR)is not feasible because in this case no different priorities could beassigned to event managers. In this case all event managers would alwayshave a priority higher then the cyclic part one. This would compromisethe time constraints of the cyclic part.

For example, in case of “fast transfer trigger from High Speed TransferSystem analog part” external event, the priority of the correspondingevent manager task is higher than the cyclic part so that, in fact, thisevent interrupts the cyclic part. In this case the event manager task iscompletely executed and then the cyclic part execution is continued.

Instead in those cases in which the event manager has to be executedwith a priority lower than the cyclic part one, the event manger task isexecuted after the end of the cyclic part.

1. A High Speed Transfer System, comprising: three Protection andControl devices; a first and a second of said Protection and Controldevices detecting a failure on a feeder bus-bar, and a third of saidProtection and Control devices comprising means for coordinating HighSpeed Transfer System functionality.
 2. A High Speed Transfer Systemaccording to claim 1, wherein said first and second Protection andControl devices communicate to the said third Protection and Controldevice via an optical cable.
 3. A High Speed Transfer System accordingto claim 2, wherein an additional digital communication channel is usedfor the a service communication among the three Protection and Controldevices.
 4. A High Speed Transfer System according to claim 1, furthercomprising a software architecture comprising a first software partwhich is performed in software cycles, and a second software part whichis performed with events.
 5. A High Speed Transfer System according toclaim 4, wherein said second software part is performed in aasynchronous way with respect to said first software part.
 6. A HighSpeed Transfer System according to claim 1, wherein each of said first,second and third Protection and Control device comprises a Human MachineInterface.
 7. An electrical distribution switchboard comprising the HighSpeed Transfer System of claim 1.